1. Field of the Invention
The present invention relates to a production process of a reaction bonded silicon carbide by infiltration of a molten silicon (Si) or silicon-molybdenum alloy (Si--Mo), and more particularly to an improved apparatus and a method thereof for manufacturing a reaction bonded silicon carbide which are capable of mass production and producing goods continuously of various sizes and characteristics by transferring a carbon preform on a carbon woven fabric and supplying a molten metal through a transfer path or a pyro-carbon coated dense graphite feeder.
2. Description of the Conventional Fabrication Method
Conventionally, since a silicon carbide has an excellent resistance to heat, wear, thermal shock, and high temperature corrosion, and high temperature strength, a silicon carbide has been studied and developed as a structural material for a ceramic engine, a gas turbine, a mechanical seal, an aerospace material, a heat-resistance brick, a ceramic filter for an incinerator, and a high temperature heat exchanger.
Most silicon carbide goods are made by a hot pressing at more than 1800.degree. C. or by a pressure loss sintering at higher than 2000.degree. C., which method has the problems that a processing itself is less economical because the sintered silicon carbide is very difficult to machine to final structure due to a high hardness of silicon carbide.
A method for manufacturing a reaction bonded silicon carbide which uses a molten silicon (or silicon-molybdenum alloy) infiltration has an advantage of obtaining desired final goods economically since by the method a poreless sintered body can be manufactured in a short time at a relatively low temperature range from 1450.degree. C. to 1600.degree. C., and the original size and shape of the preform remains unchanged even after reaction sintering.
In this method, the reaction bonded silicon carbide has the disadvantage that because the application temperature used is limited to below 1400.degree. C. due to the remaining silicon. However, since the reaction bonded silicon carbide has excellent structural material characteristics such as corrosion resistance, high temperature strength, light weight, abrasion resistance, and thermal shock, and sintered silicon carbide materials are used in a temperature below 1200.degree. C., an application range of the carbonized reaction sintered body can be used instead of sintered silicon carbide.
In addition, to increase the application temperature of reaction bonded silicon carbide, reaction bonded silicon carbide has been developed that silicon-molybdenum alloy instead of silicon is infiltrated into carbon or carbon preform forming a Mo--Si intermetallic compound instead of remaining silicon.
The above-described conventional fabrication process for a reaction bonded silicon carbide includes a technique for obtaining a poreless reaction bonded silicon carbide by infiltration of a molten silicon (or silicon-molybdenum ally) into a porous carbon preform in which the carbon is in the shape of a particle, a fiber, or a whisker. Therein, the molten silicon (or silicon-molybdenum alloy) is infiltrated through the pore in the carbon preform a capillary force, and sintered, thereby forming a silicon carbide by the reaction with the carbon therein. Here, the reaction sintered body includes silicon carbide and the remainder of silicon or silicon molybdenum. As describing permeation methods for a molten silicon (or silicon-molybdenum alloy), there are known U.S. Pat. Nos. 3,205,043, 3,325,346, 3,348,967 4,240,835 5,079,195 4,626,516 4,737,328.
The conventional fabrication processes for reaction bonded silicon carbide sintered body include a method of heating silicon (or silicon-molybdenum alloy) above melting temperature with a carbon preform under high vacuum or inert atmosphere, or a method of infiltration of a molten metal into a carbon preform through a carbon woven fabric by heating the carbon preform and silicon (or silicon-molybdenum alloy) on the carbon woven fabric.
Also, there is a method described in U.S. Pat. No. 4,626,516 in which carbon preform is placed in a melting container for silicon which has a hole for infiltration of a molten silicon, the hole and the carbon preform are connected with carbon fibers, and then the molten silicon is infiltrated into the carbon preform through capillary action.
As described above, since the conventional fabrication method for a reaction bonded silicon carbide uses a batch process wherein a high vacuum or sufficiently inert atmosphere must be maintained to prevent interruption of the infiltration process due to oxidation of the molten silicon (or silicon-molybdenum alloy), the process cost is high and not economical especially for achieving mass production of large-sized reaction bonded silicon carbides.
In the fabrication method of a reaction bonded silicon carbide, since it requires a few to tens of minutes to produce a silicon carbide synthesis by the infiltration and reaction of molten silicon (or molten silicon-molybdenum alloy), it has been anticipated to develop a more economical fabrication process for a reaction bonded silicon carbide in which the continuous infiltration of a molten silicon (or molten silicon-molybdenum) can be performed, and to meed such anticipation, there is disclosed in a British patent GB 2,227,483A, an example of a continuous fabrication process for a reaction bonded silicon carbide in which reaction bonded silicon carbides are continuously manufactured by developing a molten silicon crucible and a heating method and passing a carbon fiber through molten silicon. But, a fabrication method for a plate-type or a tube-type reaction bonded silicon carbide has not yet been developed.